Книга_953_Библиотеки_им_академика_М_И_Перельмана

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S2stimulationresultsinaclamp-likecontractionoftheperinealmuscles andanoutwardrotationoftheipsilateralleg.

S3stimulationleadstocontractionofthelevatoraniandexternalanal sphincter,resultinginabellows-likemovementandcircularcontraction

oftheanus,alongwithplantarflexionofthefirstandsecondtoes. S4stimulationproducesabellows-likecontractionofthelevatoraniand

circularcontractionoftheanuswithoutanymovementofleg,foot,or toe.

Concomitantreactionsoftheleg/foot/toecanbeobserved,butarenot essential.Theirpresencedonotindicateasuperiorpositionofthe

electrodeorabetterclinicaloutcome.Withtheforamenelectrodeinan idealposition,concomitantmotorreactionofthetoesshouldonlyoccur withhigherstimulationintensitythanthepelvicmusclereaction.

Ifasensoryresponseisusedtoguidetheplacementoftheelectrode,it canrangefromatingling“pins-and-needles”sensationtotheperception ofacontractingmuscleintheperianal,anal,perineal,orvaginalarea.

Theelectrodepositionisoptimalwhenthemotor/sensoryresponseis mostpronouncedandtheappliedcurrentislowest.

IfacutePNEsuccessfullyelicitstherequiredreaction,anelectrodeis insertedforsubchronicPNE.Therefore,theinnerstyletoftheneedle electrodeisremovedwhilekeepingtheneedlesheathintheposition.

p.127

p.128

SubchronicPNE

Twotechnicaloptionsareavailableforassessingtheclinicaleffectof temporarystimulationbeforepermanentimplantation:

leads)(Medtronic041830,TemporaryScreeningLead),whichis removedattheendofthetrialperiod.

(Seldingertechnique)withtheaidoffluoroscopy.Iftestingisclinically successful,thiselectroderemainsinplaceforpermanentstimulation. Thisprocedureisstage1ofthe“two-stageimplant.”

AfteracutePNE,theneedlestyletisremoved,buttheneedlesheath staysinplace.

Foratemporaryelectrode,itwillbeinsertedthroughthesheathofthe placedneedleelectrodeandmaneuveredtotheappropriatesacralnerve.

Intermittentstimulationisusedtoconfirmpositioning.Thesheathis thenwithdrawnandtheelectrodeissecuredbyadhesivedressingandits positionisagainconfirmedbystimulationandradiography,either intraoperativelywithfluoroscopyorpostoperativelywithatwo-plane sacralradiographorfluoroscopy.

Ifthe“two-stage”optionisused,anintroducerguideisplacedafter placingastyletthroughthesheathoftheneedleelectrodeandremoving

thesheath,todirecttheplacementofthequadripolartinedlead electrode(detailsaregivenbelow).

Forscreening,bothtypesofelectrodesareconnectedwithanextension cabletoanexternalpulsegenerator(MedtronicVerify)(Figs.17-5and

17.6).The“two-stage”optionhasanextensioncableconnectedtothe

electrodeatthelocationofthefutureplacementoftheINSandtunneled percutaneously,usuallytoasiteremotefromthefuturepositionofthe INS(mostcommonlythecontralateralside)(Fig.17-6).Asteriledressing isusedtodecreasetheriskofinfectionattheskinorperforationofthe extensioncableduringthecourseoftheteststimulation.

FIGURE17-5Teststimulationwithtemporaryelectrode

connectedtoanexternalpulsegeneratorwithgroundpad.

FIGURE17-6Teststimulationwithtinedleadelectrode

connectedwithanextensioncabletoanexternalpulse generator.Nogroundpadneeded.

StimulationSetting

Withtemporaryelectrodes,onlyunipolarteststimulationwiththe externalstimulatorispossible.Theparametersusedarethesameasfor permanentstimulation(seethefollowing).Ifmultipletemporary electrodeshavebeenplaced,theonewiththebestsensory/motor responseandthelowestthresholdischosen.Attheendofthescreening phase,thepercutaneouslyplacedtemporaryteststimulationleadis removed,andapermanentsystemconsistingofanelectrodeandINSis implanted.Thisstepisusuallyperformedseveralweeksafterscreeningto ensureintactskinconditions.

Ifatinedleadhasbeenplacedasthefirststageinthetwo-stage procedure,uni-orbipolarstimulationcanbeappliedbysettingthe

externalpulsegeneratoraccordingly;bipolarstimulationispreferred.If thetestissuccessful,thepercutaneousextensionisremovedandonlythe INSisadded(thesecondstageofthetwo-stageimplant).Ifthetestfails, thetinedleadisremovedbyanoperativeintervention:theelectrodeis extractedafteraskinincisionandexposureofitsentranceintothesoft tissuecoveringthesacrumdorsally.Fluoroscopyisadvisedtoensurethe completeremovaloftheelectrode.

Duringtheteststimulation,patientsareinstructedtointerrupt stimulationonlyfordefecationandmicturition.Bowelhabitsare documentedwithstandardizedboweldiariesandcomparedwith similarlydocumentedpretreatmentlevels.

PermanentImplant

Whenteststimulationdemonstratesa50%improvementinsymptomsby eitherdiaryorincontinencescore,permanentSNSisusuallyconsidered.

TheelectrodeisinsertedwithaminimallyinvasiveSeldingertechnique. Intraoperativeneurostimulationandfluoroscopyareusedfordirect

placement.Theelectrodeisequippedwithacurvedstyletresultingina slightlybendedbenttipoftheelectrode.

Afterpositioningtheneedleelectrodeclosetothesitewherethetarget nerveentersthepelviccavity,theneedleisremoved,leavingthesheath

inplace;throughthisastyletisplacedtoguideanintroducer.Toenter theskinwiththeintroducer,usuallyaskinincisionisplaced.This incisionshouldbesufficientlylongtoadequatelycoverandburythe electrode,whichisbentinthisposition.Thedepthoftheintroducer placementisguidedbystimulationandfluoroscopy.Thetipofthe introducershouldnotbebeyondtheventralborderofthesacrum. Subsequently,theradiopaquemarkerclosetothetipiswithinthesacral foramen(Fig.17-7).

Oncetheintroducerisintherequiredposition(tipoftheintroducerat theventralborderofthesacrum,radiopaquemarkerinthesacral

foramen),thestyletisremovedandthetinedleadquadripolarelectrode leadispushedin(Fig.17-7).Forinsertionoftheelectrodeintothe introducer,thecurvedtipoftheelectrodeshouldpointinthedirection ofthenaturalpathofthesacralspinalnerveafterexitingtheforamen: caudolateral.Itisadvisedtoinsertandmovetheelectrodeunder continuousfluoroscopytomonitoritsintroductionanditspositioning intothepelvis.Anoptimallyplacedelectrodehasaspecificappearance inthelateralimagingofthesacrum:thedistancesbetweenthemore distalelectrodecontactsappeartobelessthanthatbetweenthemore ventralonesbasedonalateraldeviationoftheelectrodefromthe

midline,whichcanbeconfirmedbyanAP(anterior-posterior)view. Theelectrodeleadhasfourelectrodecontacts,eachofwhichcanbe

individuallystimulated.Intermittentstimulationandimagingoptimize positioning.Ideally,theelectrodeshouldbeparalleltothenerve(Fig.17-

8)inacaudolateralpositionwithallfourcontactsresultinginan

adequatemotor/sensoryresponseatlow-amplitudestimulation.The introducerpermitsonlyventralordorsalmovement,theelectrodecan berotatedifadifferentdirectionisrequired.Theprocedureshouldbe restartedwiththeneedleelectrodesplacedatadifferentangle,ifneeded.

Whenpositioningisoptimal,theelectrodeisanchored:theintroduceris gentlywithdrawnandthetinesoftheleadunfoldtofixtheelectrodein

thesurroundingtissues(Fig.17-9).Continuousfluoroscopyduring withdrawaloftheintroducerhelpstoavoidunintendedinwardpushof theelectrode.

Thepulsegenerator(INS)isthenplacedinasubcutaneouspocket,most commonlyinthebuttock,medialtothedorsalaxillaryline,distantfrom

prominentbonestructures,suchastheiliaccrest.Thepositionshouldbe preoperativelydiscussedwiththepatientandmarked.Theskinincision andthesubcutaneousdissectionforthepocketshouldbelargeenough tocovertheINS,butnotsowideastopermitdevicerotation.Position abovetheScarpasfasciaisadvised.Inpatientsunabletoreacharound thebuttockstoplacethehandheldprogrammerabovetheINS,the pocketcanbeplacedintheabdominalwall.

Theelectrodeortheconnectingcableistunneledwithatunnelingdevice ofthepositionoftheINS.Careshouldbetakentoavoidproximityofthe

electrode/connectingcabletracktobonystructures.Ifatinedelectrode hasbeenusedforteststimulation,itwillremaininplaceandbe connectedaftertheremovalofthepercutaneousextensionthat connectedittotheexternalpulsegenerator.

Afterconnectionwiththeelectrode/connectingcable,theINSisburied inthepocketbutshouldnotbesuturedtothemuscle.Redundant

connectingcable/electrodeshouldbeplacedaroundorbehindtheINS, butnotinfrontofittoavoidinterferencewithprogramming.TheINS pocketisclosedwithasubcutaneousandskinlayerofsutures.

FIGURE17-7Insertionofthetinedleadelectrode

throughtheintroducer.Performedwithfluoroscopy.

FIGURE17-8A.Positionoftheelectrode:schematic

drawing.B.X-ray,anteroposteriorview.C.Positionofthe electrode:schematicdrawing.D.X-ray,lateralview.

FIGURE17-9Tinedleadfixed.

DuringtheoperativeplacementoftheelectrodeandtheINS,the electrode’spositioncanaccidentlybechangedbyanymanipulation. Repeatedstimulationisrecommendedtoensurethatthishasnot occurredandtoconfirmthefunctionofthevariousimplantedhardware components.

Bilateralimplantationofforamenelectrodesisuncommon;ithasbeen provennottobemoreeffectivethanunilateralstimulation.

POSTOPERATIVEMANAGEMENT

TheINSandelectrodeshouldbepermanentlyimagedtoserveasa referenceifcomplicationsoccurandpossibledislodgementissuspected.

Thepulsegeneratorisactivatedearlyinthepostoperativecourse, usuallyonthedayofthesurgery.Patientsshouldbeabletocooperate

becausetheprogrammingislargelybasedontheirperceptionofthe stimulationeffect.

Forthescreeningphase,unipolarstimulationisappliedasmentioned earlier,iftemporaryelectrodesareused:usuallyfrequencyof14Hz,

pulsewidthof210μs,andcontinuousstimulation.Theintensityis directedbypatientperception:mostcommonly,atingling,twitching sensationintheanal,perianal,orthevaginalarea(oracombination).

Forscreeningwithatinedleadelectrode,bipolarstimulationcanbe appliedwiththeexternalpulsegenerator,andthecontactelectrodeson

thetinedleadareprogrammedaccordingly. ForpermanenttherapeuticSNS,programmingisbasedonthefollowing

principles. Eachofthefourelectrodecontactsofthetinedleadcanbeprogrammed

asanode,cathode,orneutral(switchedoff).Inaddition,thepulse generatorcanbeprogrammedasanodeorneutral.

Bipolarstimulationispreferredtounipolarstimulation. Programmingshouldbestructuredanddocumented,followingan

algorithmintheselectionofthebestparameters. Theelectrodecombinationmosteffectivewithregardtotherequired

intensityandthepatient’sperceptionofsensationormusclecontraction oftheperineumandanalsphincterischosenforpermanentstimulation andhascommonlybeenfoundtobe:pulsewidth,210μs;frequency,15 Hz;cyclic(e.g.on:off,5:1seconds),orcontinuousstimulation. Parametersettingisdonewiththeprogrammerbytelemetry(Fig.17-

10).

Theintensityofstimulationisusuallyadaptedtobeabovetheindividual patient’sperceptionofmuscularcontractionorperianalsensationandis

adjustedifnecessary.Subsensorythresholdstimulationhasbeenshown tobeeffectivealso.

Patientsareinstructedtointerruptstimulationwiththehandheld programmeronlyfordefecationandmicturition.Urinarysideeffects

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31.08.202630 Мб0Книга_949_Библиотеки_им_академика_М_И_Перельмана.pdf
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30.08.202666 Мб0Книга_95_библиотеки_им_акад_М_И_Перельмана.pdf
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30.08.202665 Мб0Книга_96_библиотеки_им_акад_М_И_Перельмана.djvu